EQ6Pro RA Scale Issiue

[peeb61]

Hi,
Just wondering if anybody has had the same issue with their EQ6 mount that I have just encountered.

The mount is plugged into a 12V 8amp converter along with a couple of 12V fans for the DSI and primary mirror fan and whilst using it last night the mount stalled on me a couple of times and after a reboot of the EQ6 mount and reset EQ6mod and my planetarium software all was good until the next stall. (Sounded like a clunk)

I have 2 x 12v Cig adaptors piggybacked, the EQ6 was plugged into the piggy backed adaptor so I changed this to the main and all was good.

I did notice the RA Scale was not moving with the mount whilst slewing, it stayed in the same spot and it is secure. (Tightend by the two grub screws)

Any ideas to why the RA Scales does not want to move/ Or does it need to move?

The scope is balanced and has around 12-14kg of load.

Many thanks
Paul

[bojan]

Yep, this is how the RA circle is designed at EQ6 (and EQ5 as well): slewing corrupts the RA setting/calibration, while tracking doesn't.
The only way to use it is never to slew with motors, but always to push to the desired coordinates manually. And just make sure the tracking is always ON.
Also be careful which scale you are using - one is for Northern, other one (with opposite markings) is for Southern hemisphere.

Or, after slewing with motors, you should always adjust the correct RA.

The problem is, RA setting circle on those mounts is essentially hour angle circle, but coupled to tracking motor to compensate for passing of time and to show RA - which doesn't change with time, but hour angle does. This is the reason why slewing should never be attempted if you want to keep the RA calibration.
To obtain the similar functionality some more advanced processor equipped electronics setting circles have, it would require very complicated mechanical solution (including differential gearbox) - far too much expensive to be practical.
Declination circle is free from issues above.

[peeb61]

Thanks Bojan,
For your informative reply, all slewing is controlled by the planetarium software, now this corruption does sound like bad news?? Hopefully, this is not the case for me.

But should this RA Scale..should it move with the slewing? Is it news of pending disaster? Or is it easily fixed?

Paul

[koputai]

The stalling will be caused by voltage drop over the cable run from the PSU to the mount. A giveaway will be the red LED on the mount flashing whilst slewing. Under normal tracking conditions the voltage drop won't be too bad, but when doing a goto slew, both drives are working hard, and along with the other devices being powered you're probably drawing 6A or more at that time.

Now, if the cable from the PSU to the mount has 0.5 ohms of resistance, then the voltage drop will be:

E = I x R, where:

E = Voltage drop
I = Current draw
R = Resistance

So,

E = 6 x 0.5 = 3 Volts!

That means your mount will be trying to run off 9 volts, at which time it will stall.

With the EQ6 Pro that I have, if a stall occurs, the slew buttons then become inactive, and to get proper control of the mount back you have to do a power cycle.

Your solution to stalls will be to either put the PSU very close to the mount so as to have a very short DC cable run, or, if the cable run must be a reasonable distance (mine is 13 metres) then you need big DC cable from the PSU to the mount. Big speaker cable etc just won't cut it, and buying a specific DC power cable by the metre in a size that will be effective will be around $30 per metre (in my 13m case). What I did was grab an old 25m 240v exension lead, cut the ends off, cut it in half, and use all three conductors from one run to be the positive, and all three of the other run to be the negative. This gets the resistance over the run down to a very low level, and even pulling 8A over 13m I have no problems with voltage drop any more, and thus, no stalls!

Cheers,
Jason.

[bojan]

Paul,
This doesn't need fixing because this is how the RA scale on EQ6 is designed. it is supposed be used in manual mode, without computer.
As I mentioned earlier, those setting circles are suitable only for manual push to coordinates.
However, if you are using planetarium software, you can forget about those mechanical setting circles - software knows where the scope is pointing at by counting steps applied to stepper motors.

The problem with setting circles reading occurs if your motors are stalled..and Jason explained what to do in this case... nothing to with setting circles.

[peeb61]

Jason,
I think you have nailed it for me...many thanks! Thinking back to my LX200 I had and I was running this off a big car battery and when the a decent slew occured the LX200 used to reboot on me.

The distance from the power supply to the mount is not far as everything is housed in a 3m x 3m rolloff but I am using the speaker grade cabling so in effect I need to upgrade this cabling to something heavier? Like you mentioned and this extention cable sounds like a go.

This is the Powersupply I purchased : http://www.itspot.com.au/12vdc-8a-switchmode-power-supply-p206478.html?utm_source=myshopping&utm_medium=cpc&utm_campaign=Car+Accessories&utm_term=12VDC+8A+Switchmode+Power+ Supply+MP3470+

I actually got mine from Jaycar but cannot find it on their website.

Paul

[peeb61]

Bonjan,
Thanks again for your thoughts and ideas, what would we do if we didn't have the internet? Wasted calls back and forth to the supplier.

You have also been a big help. I will follow these leads and see how I go.

Paul

[keni]

This is the Powersupply I purchased : http://www.itspot.com.au/12vdc-8a-switchmode-power-supply-p206478.html?utm_source=myshopping&utm_medium=cpc&utm_campaign=Car+Accessories&utm_term=12VDC+8A+Switchmode+Power+ Supply+MP3470+

I actually got mine from Jaycar but cannot find it on their website.

Hi Paul,
I bought that one too.
Then when I wanted another I was told it had been replaced by this one:
http://www.jaycar.com.au/productView.asp?ID=MP3575&form=CAT2&SUBCATID=1000#12

I bought it and it seems to work as well as the other one.

Cheers,
Ken.

[peeb61]

Nice one Ken,
Thanks for pointing it out, thought I was going mad because I couldn't find it. It's perfect for the job now to upgrade the cabling.

Paul

[peeb61]

Hi,
I just thought I'd post an update. I have moved the 240v to 12v closer and bypassed the speaker wire by connecting to it directly and mounted a 3x 12v socket adaptor to take the EQ6 mount and the other bits. I fired everthing up and started some heavy duty slewing and watching the red panel light on the mount, the mount never missed a beat. So far so good and confidence is growing.

Many thanks for the ideas.

Paul

[Merlin66]

Just to add:
I now use a car computer transformer 12V to 15V, 140W to drive the NEQ6pro from the 12V 20Ah gel cell batteries. I got the original from Jaycar ( the latest one is from Maplins UK)
Works 100% never misses a beat.